In the electronics art, it is well known that some semiconductors can be destroyed when voltages provided to them by a power supply go above or below a relatively narrow range of voltages. Microprocessors, microcontrollers and digital signal processors are especially vulnerable to power supply over voltages and under voltages and when such devices are used to control motor vehicles and industrial equipment, the real cost of a processor's failure due to an over voltage or an under voltage can be far more costly than the replacement cost of the processors themselves. In electronic systems, which can comprise many semiconductor devices and/or one or more processors, under voltages and over voltages can place an entire system in an indeterminate state.
It is also well known that many processors include their own power internal supply voltage monitoring circuitry. The prevailing practice has been to rely on such circuitry to determine whether a power supply voltage is too high or too low.
While prior art approaches for guarding against a power supply under voltage or over voltage might be adequate for most embedded systems, in applications where safety is paramount, such as in transportation control systems, the prior art approach to monitoring power supply voltages using processor-internal circuits can be inadequate. An apparatus and method for monitoring a power supply voltage and, detecting under voltage as well as over voltage would be an improvement over the prior art.